The storm’s maximum sustained winds are estimated at about 101mph.
It will bring heavy rains, creating a risk of severe flooding as well as landslides and is expected to hit Zhejiang province and northern parts of neighbouring Fujian province late on Sunday.
Shanghai is also in the path of the storm.
Forecasters predicted that areas could see 200-400 mm (7.9–15.7in) of rainfall over the next few days.
National authorities declared a level III emergency response, the second-lowest level.
Many tourist destinations in Zhejiang have been closed Saturday and Sunday, as well as all water-based activities, including ferries and cruises.
Authorities in the city of Ningbo, one of the province’s largest, ordered schools and other educational facilities shut this weekend and all water-related activities to halt.
Some 800 ships are docked at the port.